| Message ID | 1509898543-11835-1-git-send-email-liran.alon@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 05/11/2017 17:15, Liran Alon wrote: > When running L2, #UD should be intercepted by L1 or just forwarded > directly to L2. It should not reach L0 x86 emulator. > Therefore, set intercept for #UD only based on L1 exception-bitmap. > > Also add BUG_ON() on L0 #UD intercept handlers to make sure it is never > reached while running L2. > > This improves commit ae1f57670703 ("KVM: nVMX: Do not emulate #UD while > in guest mode") by removing an unnecessary exit from L2 to L0 on #UD > when L1 doesn't intercept it. > > In addition, SVM L0 #UD intercept handler doesn't handle correctly the > case it is raised from L2. In this case, it should forward the #UD to > guest instead of x86 emulator. As done in VMX #UD intercept handler. > This commit fixes this issue as-well. > > Signed-off-by: Liran Alon <liran.alon@oracle.com> > Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com> > Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > --- > arch/x86/kvm/svm.c | 4 +++- > arch/x86/kvm/vmx.c | 9 ++++----- > 2 files changed, 7 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index 0e68f0b3cbf7..1c7f76a417e7 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -1221,7 +1221,8 @@ static void init_vmcb(struct vcpu_svm *svm) > set_dr_intercepts(svm); > > set_exception_intercept(svm, PF_VECTOR); > - set_exception_intercept(svm, UD_VECTOR); > + if (!is_guest_mode(&svm->vcpu)) > + set_exception_intercept(svm, UD_VECTOR); > set_exception_intercept(svm, MC_VECTOR); > set_exception_intercept(svm, AC_VECTOR); > set_exception_intercept(svm, DB_VECTOR); This is not called on every vmexit. The right place to touch is recalc_intercepts. Then on vmexit it will be automatically restored when nested_svm_vmexit calls copy_vmcb_control_area. > @@ -2188,6 +2189,7 @@ static int ud_interception(struct vcpu_svm *svm) > { > int er; > > + BUG_ON(is_guest_mode(&svm->vcpu)); > er = emulate_instruction(&svm->vcpu, EMULTYPE_TRAP_UD); > if (er != EMULATE_DONE) > kvm_queue_exception(&svm->vcpu, UD_VECTOR); > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 95a01609d7ee..5e2c47dd0c83 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -1878,7 +1878,7 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu) > { > u32 eb; > > - eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR) | > + eb = (1u << PF_VECTOR) | (1u << MC_VECTOR) | > (1u << DB_VECTOR) | (1u << AC_VECTOR); > if ((vcpu->guest_debug & > (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)) == > @@ -1896,6 +1896,8 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu) > */ > if (is_guest_mode(vcpu)) > eb |= get_vmcs12(vcpu)->exception_bitmap; > + else > + eb |= 1u << UD_VECTOR; It's a nit, but since you have to send a v2, I'd prefer to keep UD_VECTOR above and clear it here. Thanks, Paolo > vmcs_write32(EXCEPTION_BITMAP, eb); > } > @@ -5881,10 +5883,7 @@ static int handle_exception(struct kvm_vcpu *vcpu) > return 1; /* already handled by vmx_vcpu_run() */ > > if (is_invalid_opcode(intr_info)) { > - if (is_guest_mode(vcpu)) { > - kvm_queue_exception(vcpu, UD_VECTOR); > - return 1; > - } > + BUG_ON(is_guest_mode(vcpu)); > er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD); > if (er != EMULATE_DONE) > kvm_queue_exception(vcpu, UD_VECTOR); >
On 06/11/17 11:27, Paolo Bonzini wrote: > On 05/11/2017 17:15, Liran Alon wrote: >> When running L2, #UD should be intercepted by L1 or just forwarded >> directly to L2. It should not reach L0 x86 emulator. >> Therefore, set intercept for #UD only based on L1 exception-bitmap. >> >> Also add BUG_ON() on L0 #UD intercept handlers to make sure it is never >> reached while running L2. >> >> This improves commit ae1f57670703 ("KVM: nVMX: Do not emulate #UD while >> in guest mode") by removing an unnecessary exit from L2 to L0 on #UD >> when L1 doesn't intercept it. >> >> In addition, SVM L0 #UD intercept handler doesn't handle correctly the >> case it is raised from L2. In this case, it should forward the #UD to >> guest instead of x86 emulator. As done in VMX #UD intercept handler. >> This commit fixes this issue as-well. >> >> Signed-off-by: Liran Alon <liran.alon@oracle.com> >> Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com> >> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> >> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> >> --- >> arch/x86/kvm/svm.c | 4 +++- >> arch/x86/kvm/vmx.c | 9 ++++----- >> 2 files changed, 7 insertions(+), 6 deletions(-) >> >> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c >> index 0e68f0b3cbf7..1c7f76a417e7 100644 >> --- a/arch/x86/kvm/svm.c >> +++ b/arch/x86/kvm/svm.c >> @@ -1221,7 +1221,8 @@ static void init_vmcb(struct vcpu_svm *svm) >> set_dr_intercepts(svm); >> >> set_exception_intercept(svm, PF_VECTOR); >> - set_exception_intercept(svm, UD_VECTOR); >> + if (!is_guest_mode(&svm->vcpu)) >> + set_exception_intercept(svm, UD_VECTOR); >> set_exception_intercept(svm, MC_VECTOR); >> set_exception_intercept(svm, AC_VECTOR); >> set_exception_intercept(svm, DB_VECTOR); > > This is not called on every vmexit. The right place to touch is > recalc_intercepts. Then on vmexit it will be automatically restored > when nested_svm_vmexit calls copy_vmcb_control_area. Agreed. My bad. Will fix in v2 of this commit. > >> @@ -2188,6 +2189,7 @@ static int ud_interception(struct vcpu_svm *svm) >> { >> int er; >> >> + BUG_ON(is_guest_mode(&svm->vcpu)); >> er = emulate_instruction(&svm->vcpu, EMULTYPE_TRAP_UD); >> if (er != EMULATE_DONE) >> kvm_queue_exception(&svm->vcpu, UD_VECTOR); >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> index 95a01609d7ee..5e2c47dd0c83 100644 >> --- a/arch/x86/kvm/vmx.c >> +++ b/arch/x86/kvm/vmx.c >> @@ -1878,7 +1878,7 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu) >> { >> u32 eb; >> >> - eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR) | >> + eb = (1u << PF_VECTOR) | (1u << MC_VECTOR) | >> (1u << DB_VECTOR) | (1u << AC_VECTOR); >> if ((vcpu->guest_debug & >> (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)) == >> @@ -1896,6 +1896,8 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu) >> */ >> if (is_guest_mode(vcpu)) >> eb |= get_vmcs12(vcpu)->exception_bitmap; >> + else >> + eb |= 1u << UD_VECTOR; > > It's a nit, but since you have to send a v2, I'd prefer to keep > UD_VECTOR above and clear it here. I think your suggestion could be problematic. In case (to_vmx(vcpu)->rmode.vm86_active == true) then we would like to intercept all exceptions and therefore not clear UD_VECTOR. This is why I preferred this approach. > > Thanks, > > Paolo > >> vmcs_write32(EXCEPTION_BITMAP, eb); >> } >> @@ -5881,10 +5883,7 @@ static int handle_exception(struct kvm_vcpu *vcpu) >> return 1; /* already handled by vmx_vcpu_run() */ >> >> if (is_invalid_opcode(intr_info)) { >> - if (is_guest_mode(vcpu)) { >> - kvm_queue_exception(vcpu, UD_VECTOR); >> - return 1; >> - } >> + BUG_ON(is_guest_mode(vcpu)); >> er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD); >> if (er != EMULATE_DONE) >> kvm_queue_exception(vcpu, UD_VECTOR); >> >
On 06/11/2017 12:02, Liran Alon wrote: >> >> It's a nit, but since you have to send a v2, I'd prefer to keep >> UD_VECTOR above and clear it here. > I think your suggestion could be problematic. > In case (to_vmx(vcpu)->rmode.vm86_active == true) then we would like to > intercept all exceptions and therefore not clear UD_VECTOR. > This is why I preferred this approach. You're right. There is this if (to_vmx(vcpu)->rmode.vm86_active) eb = ~0; but of course it would not take care of #UD due to where the line is placed. You could either move the "if" at the end, or rewrite it as if (to_vmx(vcpu)->rmode.vm86_active) { vmcs_write32(EXCEPTION_BITMAP, ~0); return; } and place it at the very beginning of update_exception_bitmap. But as I said, it's just a nit and I'm okay with the code as is. Thanks, Paolo
On 05/11/2017 17:15, Liran Alon wrote: > When running L2, #UD should be intercepted by L1 or just forwarded > directly to L2. It should not reach L0 x86 emulator. > Therefore, set intercept for #UD only based on L1 exception-bitmap. > > Also add BUG_ON() on L0 #UD intercept handlers to make sure it is never > reached while running L2. ... and please make this WARN_ON_ONCE(1) instead. It's very wrong but also harmless to hit the #UD handlers, so it's not necessary to hang the whole host hard. Paolo
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 0e68f0b3cbf7..1c7f76a417e7 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1221,7 +1221,8 @@ static void init_vmcb(struct vcpu_svm *svm) set_dr_intercepts(svm); set_exception_intercept(svm, PF_VECTOR); - set_exception_intercept(svm, UD_VECTOR); + if (!is_guest_mode(&svm->vcpu)) + set_exception_intercept(svm, UD_VECTOR); set_exception_intercept(svm, MC_VECTOR); set_exception_intercept(svm, AC_VECTOR); set_exception_intercept(svm, DB_VECTOR); @@ -2188,6 +2189,7 @@ static int ud_interception(struct vcpu_svm *svm) { int er; + BUG_ON(is_guest_mode(&svm->vcpu)); er = emulate_instruction(&svm->vcpu, EMULTYPE_TRAP_UD); if (er != EMULATE_DONE) kvm_queue_exception(&svm->vcpu, UD_VECTOR); diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 95a01609d7ee..5e2c47dd0c83 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1878,7 +1878,7 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu) { u32 eb; - eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR) | + eb = (1u << PF_VECTOR) | (1u << MC_VECTOR) | (1u << DB_VECTOR) | (1u << AC_VECTOR); if ((vcpu->guest_debug & (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)) == @@ -1896,6 +1896,8 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu) */ if (is_guest_mode(vcpu)) eb |= get_vmcs12(vcpu)->exception_bitmap; + else + eb |= 1u << UD_VECTOR; vmcs_write32(EXCEPTION_BITMAP, eb); } @@ -5881,10 +5883,7 @@ static int handle_exception(struct kvm_vcpu *vcpu) return 1; /* already handled by vmx_vcpu_run() */ if (is_invalid_opcode(intr_info)) { - if (is_guest_mode(vcpu)) { - kvm_queue_exception(vcpu, UD_VECTOR); - return 1; - } + BUG_ON(is_guest_mode(vcpu)); er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD); if (er != EMULATE_DONE) kvm_queue_exception(vcpu, UD_VECTOR);
When running L2, #UD should be intercepted by L1 or just forwarded directly to L2. It should not reach L0 x86 emulator. Therefore, set intercept for #UD only based on L1 exception-bitmap. Also add BUG_ON() on L0 #UD intercept handlers to make sure it is never reached while running L2. This improves commit ae1f57670703 ("KVM: nVMX: Do not emulate #UD while in guest mode") by removing an unnecessary exit from L2 to L0 on #UD when L1 doesn't intercept it. In addition, SVM L0 #UD intercept handler doesn't handle correctly the case it is raised from L2. In this case, it should forward the #UD to guest instead of x86 emulator. As done in VMX #UD intercept handler. This commit fixes this issue as-well. Signed-off-by: Liran Alon <liran.alon@oracle.com> Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> --- arch/x86/kvm/svm.c | 4 +++- arch/x86/kvm/vmx.c | 9 ++++----- 2 files changed, 7 insertions(+), 6 deletions(-)